The invention concerns a procedure for producing low nicotine tobacco by means of high pressure extraction of the nicotine, using a compressed gaseous solvent, as well as subsequent increase of the filling volume of the tobacco.
By means of various gaseous solvents under high pressure, it is possible to remove a significant portion of the nicotine from tobacco. The applied pressures can be so high that the solvents are in the liquid or in the overcritical condition. DE-OS No. 20 43 537 cites e.g., CO.sub.2, N.sub.2 O and Ar as suitable gaseous solvents. The disadvantage of this procedure is that in addition to the nicotine, other substances are partially extracted as well, e.g., those creating the aroma. According to a procedure known from the DE-OS No. 21 42 205, this disadvantage is avoided by extracting the aroma substances separately, prior to the de-nicotinization and adding these aroma substances back to the tobacco after extracting the nicotine. This procedure is relatively costly, and the possibility cannot be excluded that the aroma substances, which are partially complicated and sensitive, are negatively influenced by such manipulations.
Another possibility to reduce the nicotine contents of tobacco products is to improve the fill volume of the tobacco used, i.e., to increase its specific volume (cm.sup.3 /g). For this purpose, the tobacco is impregnated with liquid or overcritical gases under pressure; subsequently, it is released and thermally after-treated by means of increased temperature. As suitable impregnation gases for this purpose, N.sub.2 or Ar are mentioned in DE-OS No. 29 03 300, liquid CO.sub.2 in U.S. Pat. No. 4,258,729.
However, these procedures for swelling the tobacco only cause approximately a doubling of the specific volume or the fill value. Thus, the nicotine contents of tobacco products pretreated in this manner can only be reduced to approximately 50 percent.